Detailed Data Description

Data were collected using the NOAA Environmental Technology Laboratory (ETL) Polarimetric Scanning Radiometer (PSR) during a series of flights flown over the three CLPX mesoscale study areas (MSAs) in February 2002 (onboard a NASA DC-8 aircraft) and in February and March 2003 (onboard a NASA/WFF P-3B aircraft). This airborne multiband conical-scanning imaging radiometer system provides multiband polarimetric brightness temperature images using AMSR-E bands, at a spatial resolution representative of the topography and vegetation cover. The PSR/A system operated in conical scanning mode at an incidence angle of 55 degrees from nadir, the same as that of the AMSR-E instrument. Table 1 provides a summary of PSR/A scanhead channels.

Table 1. PSR/A scanhead imaging bands, polarizations, and beam-widths

Band (GHz)

Polarizations

Beamwidth1

Δ Trms (K)2

10.6 - 10.8

v,h

8°

0.49

18.6 - 18.8

v,h

8°

0.49

21.4 - 21.7 (H2O)

v,h

8°

0.49

36 - 38

v,h

2.3°

0.14

86 - 92

v,h

2.3°

0.14

9.6 - 11.5 uµm IR

v+h

7°

0.43

1 Half-power beamwidth2 18 msec equivalent integration time, v & h

In 2002, PSR imaging occurred during both low altitude (~14,000 - 15,000 ft MSL, ~2.3 km AGL [above ground level]) and high altitude (~33,000 - 39,000 ft MSL, 9 km AGL) flight lines over the three CLPX MSAs. In 2003, PSR imaging occurred at low altitude (~14,000 - 15,000 ft MSL [mean sea level], ~2.3 km AGL), except on the first day when, in order to avoid flying within the cloud, the P-3 climbed to 3.93 km AGL. Seven flight lines were flown over each MSA every time it was visited.

Table 2 summarizes the IOP1 flights in February 2002, and the IOP3 and IOP4 flights during February and March 2003.

Table 2. Summary of CLPX PSR Flights

Exp. Name

MSA(s)
Imaged

Date

Obs. Times
(UTC)

Tot. # of
Fl. Lines

Avg. Fl. Alt
(km AGL)

3 dB Resolution
Range (m) at
37 and 89 GHz

3 dB Resolution
Range (m) at
10, 18 and 21 GHz

CLPX02
(IOP1)

RE

2/19/02

21:18-22:35

7

2.45

88 - 209

308 - 728

F

2/21/02

16:45-17:59

7

2.23

55 - 234

191 - 812

RE

2/21/02

18:09-18:25

2

2.45

88 - 209

308 - 728

NP

2/21/02

18:32-18:49

2

2.22

54 - 203

184 - 708

NP

2/23/02

17:30-18:34

7

2.22

54 - 203

184 - 708

RE

2/23/02

17:06-17:23

2

2.45

88 - 209

308 - 728

F

2/23/02

16:37-16:57

2

2.23

55 - 234

191 - 812

CLPX03A
(IOP3)

NP

2/22/03

18:35-20:35

7

3.93

184 - 334

642 - 1161

NP, RE, F

2/23/03

17:35-21:37

21

2.18

65 - 215

229 - 749

NP, RE

2/24/03

20:30-23:05

14

2.22

71 - 206

246 - 718

NP, RE, F

2/25/03

17:30-21:00

21

2.18

65 - 215

229 - 749

CLPX03B
(IOP4)

NP, RE, F

3/25/03

17:50-22:05

20

2.18

65 - 215

229 - 749

NP, RE, F

3/30/03

18:10-22:30

22

2.18

65 - 215

229 - 749

NP, RE, F

3/31/03

17:50-21:50

21

2.18

65 - 215

229 - 749

RE = Rabbit Ears, F = Fraser, NP = North Park

Figures 1-3 show flight tracks, and the terrain traversed, during the three sorties on 19, 21, and 23 February 2002 during IOP1. Each flight line (marked in red) was assigned a serial number during data processing, and those numbers are indicated in black numbers on the figures. The serial numbers are used in the data filenames. Figures 4-7 show flight tracks for the four IOP3 sorties, and Figures 8-10 show flight tracks for the three IOP4 sorties.

On 30 March 2003, two additional flight lines were flown over the Rabbit Ears MSA. Those two lines were flown at a 30º and 10º incidence angle from nadir, instead of the standard 55º. The serial numbers of these two lines are 0213 and 0214, respectively, in Figure 9.

The following tables are flight catalogs of the PSR flight lines over the CLPX MSAs, and provide a description of maneuvers listed by PSR serial number. The tables include the maneuver ID assigned to a given maneuver by the PSR processing system, date, UTC time (start and stop), and position (start and stop). Flight catalog tables are also provided as tab-delimited ASCII files with the data.

The maneuver ID consists of several fields of information separated by dots. For example, the maneuver ID CL02.DF006.M600.SLH.T has the following interpretation:

PSR/A data are available as MATLAB® files (*.mat) and binary files (*.bin) with associated ASCII headers. Missing data are identified by "-9999". All brightness temperatures are calibrated, and are in Kelvin. The data are geolocated with respect to 30-m resolution USGS terrain elevation data.

MATLAB files (e.g., L23Gqassss.mat, where ssss is the maneuver serial number) contain data organized in the following manner:

Table 3. Data type (order of variables in the third dimension).

Data Plane

Description

sceneL23Gqa(:,:,1)

10.7 GHz vert. polarization brightness temperature (TB)

sceneL23Gqa(:,:,2)

10.7 GHz horz. polarization brightness temperature (TB)

sceneL23Gqa(:,:,3)

18.7 GHz vert. polarization brightness temperature (TB)

sceneL23Gqa(:,:,4)

18.7 GHz horz. polarization brightness temperature (TB)

sceneL23Gqa(:,:,5)

21.5 GHz vert. polarization brightness temperature (TB)

sceneL23Gqa(:,:,6)

21.5 GHz horz. polarization brightness temperature (TB)

sceneL23Gqa(:,:,7)

37.0 GHz vert. polarization brightness temperature (TB)

sceneL23Gqa(:,:,8)

37.0 GHz horz. polarization brightness temperature (TB)

sceneL23Gqa(:,:,9)

89.0 GHz vert. polarization brightness temperature (TB)

sceneL23Gqa(:,:,10)

89.0 GHz horz. polarization brightness temperature (TB)

sceneL23Gqa(:,:,11)

GPS altitude (feet)

sceneL23Gqa(:,:,12)

Time stamp (sec from the beginning of the day)

sceneL23Gqa(:,:,13)

Pixel terrain geolocated latitude (dd.ddd)

sceneL23Gqa(:,:,14)

Pixel terrain geolocated longitude (dd.ddd)

sceneL23Gqa(:,:,15)

Terrain height (m) at the pixel lat/lon

Additional variables present in each of the PSR/A CLPX02/IOP1 level 2.3Gqa files are:

ssn

Serial number of maneuver (see CLPX02/IOP1 data flight catalog)

firstday

Julian day on which the flight began

scanhead

Type of PSR scanhead (e.g., PSRA for CLPX02/IOP1)

description

Text string indicating PSR maneuver ID

Binary files (e.g., L23Gqassss.bin) contain data written out as a line of sequential points in the order described for the MATLAB files. Each binary file has an ASCII header file (e.g., L23Gqassss.txt) associated with it. An example of the ASCII header file follows:

Data are provided in directories by IOP (CLPX02 [IOP1], CLPX03A [IOP3], and CLPX03 [IOP4]). Subdirectories are named for the year, month, and date. For example, 2002_0219 is the directory for 19 February 2002. Within each directory, data files are named L23Gqassss.bin, L23Gqassss.mat, and L23Gqassss.txt, where ssss corresponds to a PSR serial number. "L23" represents Level2.3 PSR data, "G" stands for geolocated PSR data, “q” represents a “quality control” identifier, and “a” stands for a subset of PSR data provided to users.

The directory “display_l23Gqa” contains the MATLAB version 6.1 m-files necessary to render brightness temperature maps from the PSR data, and a file “ReadPSRBin&TxtFile.m” that shows the necessary steps to read a binary data file using MATLAB software. Information about using these files is given in the Software and Tools section of this document.

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File Size

Files range in size from 1.9 to 8.7 MB. Header files are 1 KB.

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Spatial Coverage

Flights were flown over the Fraser, North Park, and Rabbit Ears MSAs of the CLPX study area. Flight lines are matched to data files in the Flight Summaries section of this document.

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Temporal Coverage

Three flights were flown on 19, 21, and 23 February 2002 during IOP1. In 2003, four flights were flown on 22, 23, 24, and 25 February (IOP3) and three flights were flown on 25, 28 and 30 March during IOP 4. There were 10 sorties with 25 passes over the MSAs, totaling 28 hours and 3 minutes of flight lines.

Sample Data Records

PSR image for 37 GHz channel on 19 February 2002 at Rabbit Ears MSA. Square in the center is the 25x25 km MSA area.

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Software and Tools

MATLAB® software and Directory Structure for displaying PSR/A data.

The directory “display_l23Gqa" contains the MATLAB version 6.1 m-files necessary to render brightness temperature maps from the PSR data, and a file “ReadPSRBin&TxtFile.m” that shows the necessary steps to read a binary data file using MATLAB software. This should aid the user in designing their own data-reading routine using different software. The calibrated 2.3Gqa data should be organized in a series of subdirectories (one for each CLPX02, CLPX03A, and CLPX03B flight) in the following manner:

experiment_directory\yyyy_mmdd\level2.3Gqa\sl\L23Gqaxxxx where:

experiment_directoryis the root name of the main directory (e.g. CLPX02)yyyy_mmddis a subdirectory indicating the year, month, and day of the beginning of data flight in UTClevel2.3Gqais a subdirectory referring to the data levelslis a subdirectory referring to straight and level maneuversL23Gqaxxxx.mat is a data file of type ".mat" corresponding to a maneuver with serial number xxxx.L23Gqaxxxx.bin is a binary data file corresponding to a maneuver with serial number xxxx. It contains data identical to the data contained in the".mat" file and is associated with the header file L23Gqaxxxx.txt.

The MATLAB data and m-files delivered to NSIDC are organized as described above, and there is a CLPXXXL23Gqa.log file in each experiment_directory. The user should create a PSR directory on their computer and copy the data files into this directory. The following two steps should then be done:

1) edit the m-file named setrootdir.m, changing the variable "rootdir" to indicate the path to the directory experiment_directory

2) modify the MATLAB path (appended) using the “set path” command to include the subdirectory of mfiles in display_23Gqa.

To run the display m-files, issue the command “mapl23Gqa” in the MATLAB command window. The program will show the available dates for display, and the user is prompted to select a particular flight code. The program then lists all available maneuvers from the selected flight code by their serial numbers, and queries the user to select which file(s) is(are) to be displayed. The user can select the maneuver(s) by either the listed ordinal number or the associated CLPX02/IOP1 maneuver serial number; for example, “sxxxx”. A group of maneuvers can be selected by indicating the range of ordinal numbers; for example, “2:13”. If more than one maneuver is selected, the program will ask if the user wants to spatially interpolate between adjacent maneuvers (e.g., using kridging) or overlay them on top of each other. If interpolation is selected, the program will automatically interpolate between the end of one maneuver and the beginning of the next. When the default option (overlay) is selected, no interpolation is performed and the data are overlaid, possibly overwriting data from previous maneuvers.

After loading the data for the selected maneuvers, the program queries the user for the channel (or set of channels) to be displayed. Several channel grouping options are provided in the command line. The next variables that can be selected are the minimum and maximum brightness temperatures for the range of the color map. If the minimum color temperature is defined by user, he/she will also be asked for the maximum; otherwise, the program will automatically assign those values. If auto-range calculation is selected, the program will attempt to fit a Gaussian probability distribution function to the brightness temperature histogram, and compute the color range individually for each channel using the Gaussian parameters along with a range factor. The range factor sets the color range relative to the mean by the indicated number of standard deviations. The range factor defaults to 0.6, but can be modified according to the needs of the user. Autocalculation is useful for scenes in which the brightness temperatures mostly fall within a narrow range of values.

The user can then display only a portion of the maneuver by selecting the scans to be displayed from all the scans available in the selected set of maneuvers. Here, for conical scanning, one full scan means one full rotation around the azimuth axis, and includes front and back looks. Next, the user can choose to produce either individual maps (i.e., one image for each channel) or a composite image of all channels and looks in a single map. Finally, the user has the option of selecting new latitude and longitude corners. If the user has installed the MATLAB Mapping Toolbox, he/she will also be asked to choose whether to include lines of individual U.S. states on the final map.

Quality Assessment

When interference occurred during calibration at either end of a flight line, it was possible that the data from either the whole line or from part of the line were out of calibration with the rest of the flight lines. When that happened, the investigators had two options: 1) change the calibrating software to look at all of the calibration during the entire flight together, and perform statistical analysis on the calibration looks to eliminate outliers and obtain uniform calibration for the entire flight, or 2) manually remove data in the flight lines that were obviously out of calibration. The first option requires effort beyond the scope of this project. Thus, in this first version of delivered PSR data, the investigators manually removed data. Table 5, showing quality control statistics, summarizes the effects of the data-removal process.

There were 10 sorties with 25 flights over the MSAs, totaling 28 hours and 3 minutes of flying time. The total number of lines was 1,560 where the number of lines was obtained by multiplying the number of flight lines by the number of data channels. During data removal, entire lines were mostly removed but, in some cases, only part of the line was removed. This happened when the calibration occurred within the line or when calibration on one end of the line was out of calibration with respect to the other end's calibration. When this occurred, the investigators counted that line as half of the line in computing the quality control statistics. The largest number of removed lines occurred in February 2003, when the weather over the MSAs was cloudy. However, in those cases, the removed lines were mostly for the 89 GHz channel (both vertical and horizontal polarization) because this channel is known to be sensitive to clouds. Vertical polarization for the 18.7 and 21.5 GHz channels was also affected, but to much lesser extent.

Table 4. Data “Quality Control” Statistics.

MSA Area

Date

Obs. Times (UTC)

Flight Duration

Tot. No. of lines*

No. of removed lines*

% removed lines

RE

02/19/02

21:18 - 22:30

1:12

70

11

15.7

NP RE F

02/21/02

16:45 - 18:50

2:05

110

8

7.3

NP RE F

02/23/02

16:37 - 18:46

2:09

110

10

9.1

NP

02/22/03

18:37 – 20:00

1:23

70

7

10.0

NP RE F

02/23/02

17:38 - 21:25

3:47

210

27

12.8

NP RE

02/24/03

20:36 - 22:58

2:22

140

23

16.4

NP RE F

02/25/03

17:30 - 20:56

3:26

210

33

15.7

NP RE F

03/25/03

17:50 - 22:17

3:27

210

10

4.8

NP RE F

03/30/03

18:12 - 22:29

4:17

220

10

4.5

NP RE F

03/31/03

17:51 - 21:46

3:55

210

8

3.8

TOTAL

28:30

1,560

147

9.4

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Data Acquisition and Processing

The PSR DC-8 configuration for CLPX 2002 (IOP1) and the NASA P-3 configuration for CLPX03A/IOP3 and CLPX03B/IOP4 used the NOAA PSR/A scanhead, operated in conical scanning mode at an incidence angle of 55 degrees from nadir (the same incidence angle as the AMSR-E sensor). During CLPX03B/IOP4, both the PSR/A and PSR/CX scanheads were installed on the P-3 aircraft. This pair of PSR scanheads provided the first full polarimetric and spectral simulation of the Aqua AMSR-E sensor.